| 1. |
- You, S., et al.
(författare)
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Vertical GaN devices : Process and reliability
- 2021
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Ingår i: Microelectronics and reliability. - : Elsevier Ltd. - 0026-2714 .- 1872-941X. ; 126
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews recent progress and key challenges in process and reliability for high-performance vertical GaN transistors and diodes, focusing on the 200 mm CMOS-compatible technology. We particularly demonstrated the potential of using 200 mm diameter CTE matched substrates for vertical power transistors, and gate module optimizations for device robustness. An alternative technology path based on coalescence epitaxy of GaN-on-Silicon is also introduced, which could enable thick drift layers of very low dislocation density. © 2021
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| 2. |
- Valcheva, E., et al.
(författare)
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Elimination of nonuniformities in thick GaN films using metalorganic chemical vapor deposited GaN templates
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 90:12, s. 6011-6016
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Tidskriftsartikel (refereegranskat)abstract
- Thick hydride vapor phase epitaxial GaN layers are grown on metalorganic chemical vapor deposited GaN template layers as well as directly on sapphire, with the aim of investigating the effect of the template on the strain relaxation and spatial distribution of free carriers in the overgrown GaN films. Spatially resolved cross-sectional micro-Raman spectroscopy, cathodoluminescence, and transmission electron microscopy show improved crystalline quality for growth on metalorganic chemical vapor deposited GaN templates. The highly doped and highly defective near-substrate layer composed of columnar domains, typically present in hydride vapor phase epitaxial GaN films grown directly on sapphire, is absent in the layers grown on templates. Consequently, this results in elimination of the nonuniformities of free electron distribution, a lower residual free carrier concentration (<1017 cm-3), and improved strain relaxation. © 2001 American Institute of Physics.
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| 3. |
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| 4. |
- Valcheva, E., et al.
(författare)
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Impact of MOCVD-GaN 'templates' on the spatial non-uniformities of strain and doping distribution in hydride vapour phase epitaxial GaN
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 82:1-3, s. 35-38
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Tidskriftsartikel (refereegranskat)abstract
- Thick HVPE-GaN layers are grown on Si-doped and undoped MOCVD-GaN 'template' layers as well as directly on sapphire, with the aim to investigate the effect of the MOCVD template on the strain relaxation and spatial distribution of free carriers in the overgrown HVPE films. Spatially resolved cross-sectional micro-Raman measurements, cathodoluminescence and transmission electron microscopy show improved crystalline quality resulting in elimination of the non-uniformities of electron distribution, a low free carrier concentration (< 1017 cm-3) as well as a significant strain relaxation effect. © 2001 Elsevier Science B.V.
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| 5. |
- Darakchieva, Vanya, 1971-, et al.
(författare)
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Anisotropic strain and phonon deformation potentials in GaN
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:19, s. 195217-
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Tidskriftsartikel (refereegranskat)abstract
- We report optical phonon frequency studies in anisotropically strained c -plane- and a -plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The anisotropic strain in the films is obtained from high-resolution x-ray diffraction measurements. Experimental evidence for splitting of the GaN E1 (TO), E1 (LO), and E2 phonons under anisotropic strain in the basal plane is presented, and their phonon deformation potentials c E1 (TO), c E1 (LO), and c E2 are determined. A distinct correlation between anisotropic strain and the A1 (TO) and E1 (LO) frequencies of a -plane GaN films reveals the a A1 (TO), b A1 (TO), a E1 (LO), and b E1 (LO) phonon deformation potentials. The a A1 (TO) and b A1 (TO) are found to be in very good agreement with previous results from Raman experiments. Our a A1 (TO) and a E1 (LO) phonon deformation potentials agree well with recently reported theoretical estimations, while b A1 (TO) and b E1 (LO) are found to be significantly larger than the theoretical values. A discussion of the observed differences is presented. © 2007 The American Physical Society.
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| 6. |
- Darakchieva, Vanya, et al.
(författare)
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Effect of anisotropic strain on phonons in a-plane and c-plane GaN layers
- 2007
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 300:1, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- We have studied phonons in two types of anisotropically strained GaN films: c-plane GaN films grown on a-plane sapphire and a-plane GaN films grown on r-plane sapphire. The anisotropic strain in the films is determined by high-resolution X-ray diffraction (HRXRD) in different measuring geometries and the phonon parameters have been assessed by generalized infrared spectroscopic ellipsometry (GIRSE). The effect of strain anisotropy on GaN phonon frequencies is presented and the phonon deformation potentials aA1 (TO), bA1 (TO), cE1 (TO) and cE1 (LO) are determined. © 2006 Elsevier B.V. All rights reserved.
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| 7. |
- Fröjdh, Christer, 1952-, et al.
(författare)
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New sensors for dental X-ray imaging
- 1999
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 434:1, s. 24-29
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Pecz, B., et al.
(författare)
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GaN heterostructures with diamond and graphene
- 2015
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Ingår i: Semiconductor Science and Technology. - : IOP PUBLISHING LTD. - 0268-1242 .- 1361-6641. ; 30:11, s. 114001-
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Tidskriftsartikel (refereegranskat)abstract
- The full performance of GaN devices for high power applications is not exploited due to their self-heating. Possible solutions are the integration of materials with high heat conductivity i.e., single crystalline diamond and graphene layers. We report the growth of single crystalline (0001)-oriented GaN thin films on (100), (110) and (111) diamond single crystals studied by transmission electron microscopy (TEM) in cross-sections. As for graphene, we show a high quality GaN layer that was deposited on patterned graphene layers and 6H-SiC. The atomic structures of the interfaces in the heterostructure are studied using aberration-corrected scanning TEM combined with energy dispersive x-ray and electron energy-loss spectroscopy.
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| 9. |
- Arnaudov, B, et al.
(författare)
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Hall effect data analysis of GaN n(+)n structures
- 2002
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 234:3, s. 872-876
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Tidskriftsartikel (refereegranskat)abstract
- We develop a model for analysis of Hall effect data of GaN structures composed of sublayers with different thicknesses and contacts placed on the top surface, We analysed the contributions of the conductivity of every sublayer of a planar sample taking into account the fact that the sample sublayers are partially connected in parallel to each other by series resistances formed in areas lying below the contacts from the upper layer. Correction factors, which reduce the contribution of the underlying layers to the measured whole sample conductivity, are obtained from the equations relevant to the respective equivalent circuit.
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| 10. |
- Arnaudov, B., et al.
(författare)
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Magnetic-field-induced localization of electrons in InGaN/GaN multiple quantum wells
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 83:13, s. 2590-2592
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Tidskriftsartikel (refereegranskat)abstract
- A study was performed on the magnetic-field-induced localization of electrons in InGaN/GaN multiple quantum wells (MQW). A stepwise behavior of both the Hall coefficient and magnetoresistivity was observed. The peculiarities were explained by a magnetic-field-induced localization of electrons in a two-dimensional (2D) potential relief of the InGaN MQW.
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